1. Field of the Invention
The present invention relates to an endoscope inserted into a space to be inspected and used for observing the space.
2. Description of the Related Art
In general, an endoscope widely used for industrial purposes comprises a flexible insertion section, which is to be inserted into a space to be inspected. The insertion section includes a bendable portion, and this bendable portion can be bent in the vertical direction, in the horizontal direction or in any desired direction, i.e., a combination of the vertical and horizontal directions. A plurality of bending-operation wires (e.g., four wires) are attached to the bendable portion. The proximal end of each bending-operation wire extends toward the proximal portion of the insertion section. An operation section is coupled to the proximal end of the insertion section. The operation section includes a bending-operation mechanism, and the proximal ends of the bending-operation wires are coupled to this bending-operation mechanism.
The operation section includes an input device, such as a joystick. The bending-operation mechanism is driven and the bendable portion is bent, using the joystick. The joystick is provided with a stick whose proximal portion is pivotally supported by a pivot support. The stick is movable between a neutral position where it stands upright and a slanted position where it is slanted. When the stick is slanted in a direction at a desired angle, signals corresponding to the direction and angle of the stick are generated. The joystick outputs signals when operated, and the driving motor or other structural elements of the bending-operation mechanism are driven in accordance with the output signals. The bending-operation wires are pulled, accordingly. In this manner, the bendable portion is bent in association with the pulling movement of each bending-operation wire when the joystick is operated. (An example of this type of endoscope is disclosed, for example, in Jpn. Pat. Appln. KOKAI Publication No. 5-15486.)
In an endoscope of the above structure, the bending-operation wires are inserted in angle coils for protection, and in this state they are arranged in the interior of the tube of the insertion section. When the bending-operation wires are pulled, they slide along the inner surface of the angle coils. When the bendable portion is bent, there is inevitably a certain degree of resistance (e.g., frictional resistance) between the bending-operation wires and the angle coils. For this reason, even if the joystick is returned to the neutral position after the bendable portion is bent in a certain direction, it may happen that the operation force will not be transmitted fully to the bendable portion. In such a case, the bendable portion may not be restored into its substantially linear state, which corresponds to the neutral position of the stick.
In the conventional art, when the bendable portion is bent and then restored into the substantially linear state corresponding to the neutral position, the operator intentionally operates the stick in the direction opposite to that in which it has been slanted. By so doing, the bendable portion can be restored into the linear state corresponding to the neutral position.
Jpn. Pat. Appln. KOKAI Publication No. 5-15486 discloses a control means for detecting the degree to which a bendable portion is bent and controlling the time for which a driving mechanism is operated until the bendable portion is restored into the linear state.
The degree to which the bendable portion is operated in the direction opposite to that in which it has been slanted and the time for which the driving mechanism should be operated, are determined by parameters. The parameters are preset for a control circuit and represent a predetermined extent.